Re: [PATCH 2/7] cfq-iosched: use appropriate run queue function

[Johannes Thumshirn <jthumshirn@suse.de>]

On Mon, Dec 05, 2016 at 08:12:16AM -0700, Jens Axboe wrote:
> On 12/05/2016 01:48 AM, Johannes Thumshirn wrote:
> > On Fri, Dec 02, 2016 at 08:15:16PM -0700, Jens Axboe wrote:
> >> For MQ devices, we have to use other functions to run the queue.
> >> No functional changes in this patch, just a prep patch for
> >> support legacy schedulers on blk-mq.
> >>
> >> Signed-off-by: Jens Axboe <axboe@fb.com>
> >> ---
> >>  block/cfq-iosched.c | 22 +++++++++++++++++++---
> >>  1 file changed, 19 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> >> index c73a6fcaeb9d..d6d454a72bd4 100644
> >> --- a/block/cfq-iosched.c
> >> +++ b/block/cfq-iosched.c
> >> @@ -919,8 +919,14 @@ static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
> >>  static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
> >>  {
> >>  	if (cfqd->busy_queues) {
> >> +		struct request_queue *q = cfqd->queue;
> >> +
> >>  		cfq_log(cfqd, "schedule dispatch");
> >> -		kblockd_schedule_work(&cfqd->unplug_work);
> >> +
> >> +		if (q->mq_ops)
> > 
> > You've introduced blk_use_mq_path() in patch 1, so why don't you use it here
> > as well?
> 
> There's a difference. q->mq_ops means "this driver is blk-mq",
> blk_use_mq_path() checks for ->elevator as well, which means "for this
> driver, allocate and insert requests via the legacy IO scheduler path".

Ah OK, that clarifies it. thanks

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